Hi,
Welcome to Q&A platform.
I noticed that the issue involves several third-party products which we're not familiar with. For the third-party related products, I would suggest you could contact the third-party technical support for further troubleshooting.
From Windows perspective, I would suggest you could test the file loading speed when a Windows client accessing the SMB files.
Meanwhile, for file loading performance issue, we usually need to analyze performance and network traffic log to find any clues. Unfortunately, analysis of performance and network log is beyond our forum support level and due to forum security policy, we have no such channel to collect user log information. So, if you want to find the cause, we recommend you open a case with MS Professional tech support service, they will help you open a phone or email case to Microsoft, so that you would get a technical support on a one-to-one basis while ensuring confidential information.
Here is the link:
https://support.microsoft.com/en-us/gp/customer-service-phone-numbers
Best Regards,
Sunny
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